The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Water control problems are ubiquitous in oil and gas reservoirs and they have many forms. One difficult problem is that of shutting off fractures or fissures in carbonate reservoirs without impacting the hydrocarbon production. The fissure or fracture tends to dominate flow to a producing well compared to the matrix flow. Commonly, the flow of hydrocarbons may move from the matrix into the fractures and from the fractures into one or more main fractures that intersect the wellbore. Because of the huge flow potential in a sizable opening, any fluid solution must be rather large in volume and able to resist extrusion after the treatment has finished and the well is placed on production. A further complication is the reservoir may contain a range of fissures, fractures and vugs, all of which have the potential to flow. Vugs have both flow potential and large storage capacity, while the capacity of fissures and fractures depend upon the width and the cementation. Since these features cannot be easily mapped, the volumes and geometry of the features are not known, leading to difficulties in designing a plugging treatment.
A similar problem has been encountered in drilling applications where lost circulation zones exist. These features tend to capture the expensive drilling fluid and must be plugged prior to continuing the drilling process. Cementing pipe in hole is subject to these features as well, and poor cementing can result because the cement is diluted by underground rivers or the fluid loss is so high that the cement cannot be propagated throughout the area requiring cement.
Various solutions exist for combating these problems and they generally are referred to as lost circulation material (LCM), lost circulation pills, plugs, gels, cement plugs, formation damage plugs, solids laden plugs, bentonite plugs, fiber plugs, etc. Some solutions include pumping water reactive materials in a non-aqueous fluid (clays and especially bentonite, organic polymers, cement) that tend to set when water is encountered; aqueous fluids that set into stiff gels (crosslinked-water soluble organic polymers, inorganic monomers that gel such as silicates and aluminum compounds, organic monomers that polymerize in situ); non-aqueous fluids such as resins; slurries of solids in aqueous or non-aqueous carrier fluids that plug indiscriminately such as walnut shells, diatomaceous earth or silica flour; and non-compatible waters which precipitate upon meeting in the reservoir.
Polymer gels have been widely used for conformance control of naturally fissured/fractured reservoirs. For an overview of existing polymer compositions, reference is made to the U.S. Pat. Nos. 5,486,312 and 5,203,834 which also list a number of patents and other sources related to gel-forming polymers.
Some of these solutions have been foamed with gas to plug a larger volume with the same amount of chemicals. Foams are often stabilized with polymers which restrict the drainage of the foam boundaries or plateau borders. Foamable gel compositions are described for example in the U.S. Pat. Nos. 5,105,884, 5,203,834, and 5,513,705, wherein the polymer content is reduced at constant volume of the composition.
The typical components of a foamable gel composition are (a) a solvent, (b) a crosslinkable polymer, (c) a crosslinking agent capable of crosslinking the polymer, (d) a surfactant to reduce the surface tension between the solvent and the gas, and (e) the foaming gas, itself.
A new gelled foam having enhanced properties of foam stability is proposed herewith.